1. Field of the Invention
The present invention relates to an image forming system and the like in which a paper feed device or a paper discharge device is connected to an image forming device such as a printer. In particular, the present invention relates to an image forming system and the like for selectively determining whether paper conveyance is continued or stopped when poor feeding of paper sheets for image formation is caused.
2. Description of the Related Art
Conventionally, when poor paper feeding such as a paper jam is caused in an image forming system in which a paper feed device and a paper discharge device are connected to an image forming device, paper conveyance is generally stopped by emergently stopping the image forming system. For example, in Japanese Patent Application Laid-open No. 2004-001511, there is disclosed a system that is provided with an emergency stop instruction means in which an external controlling device gives an instruction for emergency stop to a printing device, and an emergency stop means in which a driving system in the printing device is stopped as soon as the instruction for emergency stop is given by the emergency stop instruction means. In this system, the external controlling device controls collectively the printing device and all optional devices which are attached to the printing device in the periphery thereof. In this system, the external controlling device stops the driving system of the printing device when something is wrong with the optional devices.
In Japanese Patent Application Laid-open No. 2002-154744, there is disclosed a system which judges whether or not residual paper sheets remaining from place to place on a conveyance path is automatically dischargeable after an emergency stop is once made. When a door of a device is opened, this system records, in a non-volatile memory, a stop position of a front edge of a recording medium at a moment when the emergency stop or a paper jam has occurred, as any one of a first section, a second section or a third section. The first section is one where the front edge is located certainly before a flapper. The second section is one where the front edge has certainly passed through the flapper. The third section is between the first section and the second section, and a section where the front edge has not yet certainly passed through just before the flapper. Next, this system determines whether or not the recording medium stopped on the conveyance path is automatically dischargeable, based on the recorded stop position of the front edge of the recording medium.
However, in the above described conventional art, a user needs to remove not only paper incapable of being conveyed but also paper remaining temporarily inside the device due to the emergency stop as the residual paper sheets. In addition, even in a system capable of automatically discharging paper sheets after the emergency stop, there is a case where it is difficult to automatically discharge the paper sheets in the emergency stop, depending on a kind of paper.
In addition, as for a method for automatic paper ejection, there is a method where all devices of an image forming device, a paper feed device, and a paper discharge device, the latter two of which are connected to the image forming device, are driven for a predetermined period in order to discharge paper sheets remaining temporarily in the device after an emergency stop of the device caused by occurrence of a paper jam. In this method, however, all the devices keep being driven for a predetermined period. Therefore, power consumption increases since the devices unrelated to the discharging operation of the paper sheets are also driven.